Cast molded lenses, such as contact lenses, are produced in cast molding cups. Cast molding cups can be understood to be lens molds formed from two mold members or mold halves. One of the mold members has a concave surface that defines an anterior surface of a lens. The other mold member has a convex surface that defines a posterior surface of the lens. To produce lenses, such as contact lenses, it is necessary to separate the two mold members (e.g., demold the molding cup or lens mold), and to separate the lens product produced in the molding cup (e.g., delens the lens product from one of the mold members).
For relatively rigid pre-hydrated lens products, such as hydroxyethylmethacrylate (HEMA)-based cast molded lens products, the polymerized lens product can be delensed by compressing a mold member with a force sufficient to overcome the attachment force between the lens product and a surface of the mold member. Due to the rigidity of the material, the material tends to favor its natural shape. Therefore, the relatively rigid lens product can be easily separated from the mold member using only compression forces. However, such methods are not useful for pre-hydrated lens products that are relatively more flexible or have a lower modulus. For example, such delensing methods do not effectively separate silicone hydrogel contact lenses or similar lens materials from mold members.
One alternative to delensing relatively flexible lens products is to soak the mold member and the lens product in contact therewith in a volume of liquid. Although lenses can be effectively separated using soaking methods, these methods require additional machinery and time which can negatively impact production of large amounts of contact lenses.
Thus, there remains a need for new delensing methods which permit flexible lens products to be separated from lens molds, and do not require liquid soaks.